Tuesday, October 6, 2009

Psychological tests I

Many doctors regard assessments based on inter­view and observation as crude and inaccurate, and feel that 'proper' tests, using more structured procedures, are essential for diagnostic precision. It is therefore worth noting that psychologists define a test as 'any systematic procedure for observing a person's behaviour and describing it with the aid of a numerical scale or a category system'.

A systematic interview or an observation session constitutes a test in terms of this definition. The important question to ask is not4 Is this test accurate enough?' but 'Will this procedure provide reliable information relevant to the problem in hand?'

When it does seem necessary to quantify one's observations accurately, a formal test procedure may be used. For example, it may be useful to decide whether a deaf child has normal intelli­gence when confronted with non-verbal tasks, or to assess how much a child's IQ has changed following a brain injury.

The mechanics of test administration are not difficult to master; the skill lies in the interpretation of the results, which calls for a knowledge of the psychological literature. For this reason, the supply of many test kits is restricted to qualified clinical or educational psychologists, who will normally be responsible for the detailed assessment of these more complex problems.

Psychological tests are designed to make systematic observations and quantify them. The results are then related to normative data; in other words, they are compared either with the individual's own previous performance or, more often, with the results obtained by a group of similar individuals. The first of these approaches is useful in, for example, planned teaching pro­grammes for children with learning disabilities, as a means of evaluating progress. The majority of the psychometric tests used in clinical assessment are of the second type, and the most familiar are those used to measure intelligence (IQ tests) and language development. Procedures are also available for the examination of personality, behaviour, brain damage, and many other factors. An important distinction is made between tests of IQ and tests of attainment, such as reading or writing.

Many psychometric tests are standardized. This means that they require a specified set of materials, the instructions and mode of presen­tation are precisely stated and the results are assessed by comparison with the known per­formance of normal children from a comparable background. The tester may of course use their discretion to depart from the specified procedure, but the more this is done, the less accurate the result will be.

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